For precise speed control in rolling mills the main drives of the roll stands and the coilers need to be equipped with an encoder. In addition, it is often necessary to provide increased protection for personnel during special operating modes, such as: For this application Johannes Hübner Giessen has been working with Motor OEMs for many decades to provide complete solution ie. Electrical and mechanical components.
Encoder retrofitted directly to the tandem drive ensures trouble-free rolling mill operations
Pilger mill in tube rolling mills - hot and cold pipe detection
- Straightforward retrofit without free shaft end
- Bearingless magnetic encoder with split pulse wheel and narrow construction
- Replacement for belt drive that required intensive maintenance
- Also suitable for high speed and rapid reversing movements
Motor shaft of a rolling mill tandem motor with mounted MAG-G system.
- Only the rear motor of tandem drives has a shaft end available to which an encoder can be attached. However, a speed signal is also required from the front motor for synchronizing purposes in tandem operations or as motor feedback in single-motor operations (decoupled mode of operation). This is often generated by an encoder driven by a toothed belt, but typical disadvantages of this solution (tension, alignment, wear etc.) have a negative impact on the quality of the signal and lead to increased servicing costs. The better solution is a special encoder that can be attached directly to the shaft of the front motor without having to separate the tandem motors.
Bearingless magnetic encoder system MAG-G with split pulse wheel and scanning head.
- To be able to mount an encoder where there is no shaft end available Johannes Hübner Giessen installed its bearingless, magnetic type encoders MAG-G. Consisting of two half shells they can be retrofi tted at any point of a rotating shaft. The staggered design of the two half shells ensures the construction is suitable for applications with high speed and rapid reversing movements. The bearingless version o ers protection against shaft currents, it is wear free and also suitable for large shaft diameters. Thanks to its slim design width of just 30 mm the MAG-G system is easy to integrate in existing solutions.
Products and Accessories
Case Study Number
- The increasing flexibility of production lines requires a high adaptability of sensors. Continually changing object geometries, different temperatures and very high radiation or surrounding temperatures are no rarity.
- In a pilger mill those rough conditions can be found, among others in the production of seemless steel pipes. The raw steel blocks, each weighing a few tons are heated up first in a round oven at a temperature of 1300 °C.
- After descaling of the surface, the steel block is prepunched in a hole press with a strength from a converted 2000 t. In the next sloping rolling mill the growing pipe rotates between two rollers that are positioned at an angle to each other. The punching is widened to the size of the mandrel diameter.
Previous solution / Competitor product
- The sensor that was installed at this application is the HMD OKA 2038.38 G with tube OL 19.
- The signal of the infrared sensors controls the movement of centering device and abutment. The point of view is restricted by the tube and prevents disturbances by steam in the cooling phase.
- An optimum adaptation to the operating conditions is given due to the adjustable response temperature. The HMD with self-learning response temperature (Auto-Teach function) is suited to continually changing conditions.
- The compact sensor with a stainless steel housing can withstand surrounding temperatures of up to 75° C. The use of a cooling jacket raises this up to 200° C.
- Alternatively sensors with fibre optic cables are available which permit an application at ambient temperatures up to 600° C without cooling.
- High temperature stability
- Recognition of hot objects at big distances
- Self adjustment with Auto-Teach or step switch for the response temperature
Product Part number
- OKA 2038.38 G
- Piros swivel stand HM2
- Tube OL 19
- Pilot light unit (for alignment) DAK 308 + OL 26
- Different cable lengths (e.g. 15 m)
compared to previous solution or competition
Other Solutions in Hot Rolling Mills – Roughing Mills